Outdrive Vent Screw - Cant break loose

Rock Hall

Rock Hall

New Member
Feb 18, 2006
163
Lancaster, PA
Boat Info
1989 Searay 220DA 5.7
Engines
Mercruiser 5.7 Alpha One Gen I
I'm having a heck of a time trying to remove the upper vent screw. I had a little elecrolysis issue last year and I guess it got to this screw. I've tried all the normal stuff. PB Blaster, Freeze Off, Bigger screw driver, Anything else I can try? I'm afraid to take a drill to it for fear of getting metal in the drive.
Any suggestions? Boat is still in driveway and slip is empty.
 
I'd say time for a little heat...go easy.
 
The vent screws were both frozen on my drives - I had to use a heat gun and then went to a smaller screwdriver which only took up half the slot and used a hammer to knock it loose. This was after PB Blaster, impact driver and a lot of choice words. Make sure you use new screws and gaskets which will make sure it seals correctly and that you can get them out next time.
 
I did try an impact driver like the one from Klein. I was thinking about an air wrench, but I'm hesitant because I could completely destroy the screw pretty fast.
I'm heading over to the dealer this morning to pick up a kicker motor, I'll see what they do. I think heat is the next thing to try. I do have a heat gun, I'll try that before the torch.
Thanks for the help. I have 2 days left to solve this problem if I want to be in the water this weekend.

Mark
 
Drill it right down the center. Find a Roberts(square drive) bit tip from a removeable driver that is pretty good size. You don't need to drill all the way through but make sure it's a small enough diameter you can get a good bite with the Roberts driver tip. Tap that in the hole firmly. Then if you have a socket with the 1/4" drive, you can provide constant even torque to get it out.
It's stainless so it may be tough to drill but with good drill bits it will cut.
Best of luck,
 
Last edited:
thanks for the suggestion. I'll try a little heat first and if no luck will try the square bit.
 
I hate to bring up this super old thread but I was attempting to change the gear lube. One drive-vent screw is completely seized on. Tried heat, impact driver, chisel etc. no way this thing is coming off. I don't think the previous owner ever took it off either. So, my plan is to fill the unit until it appears in the gear lube monitor, then just top off the monitor. Other than that I can not see a way to remove the screw without drilling which is risky give the screw is stainless and the drive is aluminum. I am thinking of having a tech do it when the seals are due to be replaced...end of next season. Any opinions or thoughts gladly accepted.
 
one of the main reasons you are changing the oil is in case there is water in there. if you just fill it, and there is water and you get a hard freeze, you are risking cracking that lower unit...

oops, i went back and reread your post. I assume you did drain it, but just can't get the vent screw off? hopefully it did completely drain without the vent screw.
 
Not sure I follow. It is the vent screw that is seized. The drain screw is fine and all oil has drained (lube looked good and had no signs of moisture). Just read back through on my thread and realized I didn't specify that I did drain and refill.

Basically buy removing the cap on the lube monitor it vented the gear lube enough to drain. Took over two hours but it drained. My concern now is if the vent screw is sealed. My instincts tell me that is based on my inability to remove it with anything short of jackhammer.
 
I've read a few posts by people who actually filled without removing the vent screw - they just kept pumping drive lube in until it started showing up in the reservoir.
 
Madifonzo said:
Not sure I follow. It is the vent screw that is seized. The drain screw is fine and all oil has drained (lube looked good and had no signs of moisture). Just read back through on my thread and realized I didn't specify that I did drain and refill.

Basically buy removing the cap on the lube monitor it vented the gear lube enough to drain. Took over two hours but it drained. My concern now is if the vent screw is sealed. My instincts tell me that is based on my inability to remove it with anything short of jackhammer.
Click to expand...

just finished winterizing a newer Mercury outboard and now understand what you are talking about. i am used to doing Yamahas, which only have 2 screws (the vent and top level are the same). So now i can see how you could get all the oil out by using the bottom drain, and the oil fill (which then would allow "venting").
 
jxg said:
just finished winterizing a newer Mercury outboard and now understand what you are talking about. i am used to doing Yamahas, which only have 2 screws (the vent and top level are the same). So now i can see how you could get all the oil out by using the bottom drain, and the oil fill (which then would allow "venting").
Click to expand...

The bottom drain and the oil fill are the same screw.
 
Westie said:
The bottom drain and the oil fill are the same screw.
Click to expand...

that i get. my yamaha has 2 screws. top (which is the level and the vent), and bottom. If you don't take the top off, you won't get all the old oil out (i guess if you let it sit a long time it will eventually drain. But I just did a friends newer merc, and it had 3 screw. bottom for fill and drain, and 2 at top, one for vent and one for level...
 
For knowledge. I did this today and it worked. Ended up removing the drives anyway for reconditioning.
 
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